Inflammation in carotid atherosclerotic plaque: a dynamic contrast-enhanced MR imaging study
William S Kerwin1, Kevin D O'Brien, Marina S Ferguson
1Department of Radiology, Division of Cardiology, and Department of Surgery, University of Washington, 815 Mercer St, Seattle, WA 98109, USA. bkerwin@u.washington.edu
Purpose:
To prospectively evaluate if there is an association between plaque enhancement at magnetic resonance (MR) imaging and proinflammatory cardiovascular risk factors and plaque content.
Materials And Methods:
This study was performed with informed consent, HIPAA compliance, and institutional review board approval. Contrast agent dynamics within carotid plaques were measured in 30 patients (29 men, one woman; mean age, 67.7 years +/- 10.7 [standard deviation]) who were scheduled to undergo carotid endarterectomy. Measurements were based on kinetic modeling of images obtained at 15-second intervals during which a gadolinium-based contrast agent was injected. The time-varying signal intensities within the plaques were used to estimate the fractional plasma volume (vp) and transfer constant (Ktrans) of contrast material into the extracellular space. Pearson correlation coefficients were computed between blinded MR measurements and histologic measurements of plaque composition, including macrophages, neovasculature, necrotic core, calcification, loose matrix, and dense fibrous tissue. Correlation coefficients or mean differences were computed regarding clinical markers of cardiovascular risk.
Results:
Analyzable MR images and histologic results were obtained in 27 patients. Measurements of Ktrans correlated with macrophage (r = 0.75, P < .001), neovasculature (r = 0.71, P < .001), and loose matrix (r = 0.50, P = .01) content. Measurements of v(p) correlated with macrophage (r = 0.54, P = .004), neovasculature (r = 0.68, P < .001), and loose matrix (r = 0.42, P = .03) content. For clinical parameters, significant associations were correlated with Ktrans only, with decreased high-density lipoprotein levels (r = -0.66, P < .001) and elevated Ktrans measurements in smokers compared with nonsmokers (mean, 0.134 min(-1) vs 0.074 min(-1), respectively; P = .01).
Conclusion:
The correlations between Ktrans and histologic markers of inflammation suggest that Ktrans is a quantitative and noninvasive marker of plaque inflammation, which is further supported by the correlation of Ktrans with proinflammatory cardiovascular risk factors, decreased high-density lipoprotein levels, and smoking.
Insights
Magnetic resonance imaging (MRI) can noninvasively assess carotid plaque inflammation. The transfer constant (Ktrans) measured by MRI correlates with histologic markers of inflammation and cardiovascular risk factors like smoking and low HDL levels.
Area of Science:
- Cardiovascular Imaging
- Medical Physics
- Biomedical Engineering
Background:
- Atherosclerotic plaques pose a significant risk for cardiovascular events.
- Identifying vulnerable plaques noninvasively is crucial for risk stratification.
- Inflammation is a key driver of plaque instability.
Purpose of the Study:
- To investigate the association between plaque enhancement on MRI and proinflammatory cardiovascular risk factors.
- To evaluate the correlation between MRI-derived plaque content and histologic markers of inflammation.
Main Methods:
- Contrast-enhanced MRI was used to measure contrast agent dynamics in carotid plaques of 30 patients.
- Kinetic modeling estimated fractional plasma volume (vp) and transfer constant (Ktrans).
- MR measurements were correlated with histologic plaque composition and clinical cardiovascular risk factors.
Main Results:
- Ktrans measurements significantly correlated with macrophage content (r=0.75), neovasculature (r=0.71), and loose matrix (r=0.50).
- Vp measurements also correlated with macrophage (r=0.54) and neovasculature (r=0.68) content.
- Elevated Ktrans was associated with decreased high-density lipoprotein levels (r=-0.66) and smoking.
Conclusions:
- Ktrans is a quantitative, noninvasive marker of plaque inflammation.
- MRI-derived Ktrans reflects histologic markers of inflammation.
- Ktrans correlates with key proinflammatory cardiovascular risk factors, including smoking and low HDL levels.
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